The Science Behind The Olympics

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SPEED SKATING

Hard Science of Ice Crystals

Forget the 4-minute mile. Shani Davis has skated 1500 meters--the "metric mile," or nearly 5000 ft.--in a world record time of 1:43.33, averaging more than 32 mph. It's all about glide, enhanced by Davis's superior body mechanics but made possible, of course, by the near-frictionless property of ice. Conventional wisdom says that the pressure of a skater's blades melts a thin layer of ice crystals, producing a lubricating layer of water. The water part is right, but as Gabor Somorjai found out, the mechanism is wrong. Somorjai, a surface chemist at the University of California at Berkeley, conducted electron diffraction studies of ice. Even at minus 240 degrees, he found that a single outer layer of molecules was rapidly oscillating, forming a "quasi-liquid" layer. As the temperature was increased, more layers of mobile molecules were added. "When you're skating, there are about 20 layers of water," Somorjai says. "This is the natural surface structure--it has nothing to do with putting pressure on it."

The challenge in bobsled is akin to the challenge in NASCAR racing: designing a vehicle that can go slightly faster, while staying within fraction-of-an-inch official specs. That's what former Daytona 500 champion Geoff Bodine realized in 1992 after watching the U.S. team extend a 36-year Olympic medal drought. He and car designer Bob Cuneo then formed Bo-Dyn Bobsleds and started building custom sleds to replace the generic imports the U.S. team was using.

One task was to reduce weight. Bo-Dyn's four-man sleds are 462.97 pounds and two-man sleds are 374.79 pounds--the minimums allowed by the rules. This leaves room under the weight cap for the biggest engines in the form of stronger, heavier athletes. But weight is only one factor.

"Just like a race car, the sled has all kinds of precise geometry in the suspension," Cuneo says. Technicians tweak the suspension, the articulations of the front runners and the middle of the sled body, and choose the optimum steel runners. The results of extensive R&D are showing: The U.S. team won three medals in the last games.

It's well-established that a ski jumper's body and skis work like an airplane wing. They direct the onrushing wind downward, forcing the air rushing over the top of the body and skis to flow faster than the air below. In a demonstration of Bernoulli's principle, this creates lower pressure on the top side of the skier than below him, pulling him upward. But ski jumpers aren't just like airplane wings--they're like airplane wings with precise controls. Austrian researchers Bernhard Schmölzer and Wolfram Müller studied competitors at the 2002 Olympics, where the jumping was held in Park City, Utah, at an unusually high altitude of more than 6500 ft. Top jumpers compensated for the decreased lift (and drag) of the thin air by adjusting the angle between their bodies and skis to an average of 16.1 degrees, greater than the 11.7 degrees seen at lower elevations. This winter's Olympic jumping events will be held at 5000 ft. in the Italian town of Pragelato.

Snowboarder Danny Kass is brilliant at improvising during his halfpipe runs, points out U.S. Olympic coach Mike Jankowski. But, some things are set the instant he launches from the lip of the 18-ft.-high pipe. The path his center of mass will take--how high he soars and where he lands--is determined by his approach. And the angular momentum for the flips and rotations he does 15 ft. off the deck must be generated before he leaves the snow. Top riders can spin through 1440 degrees (four rotations), but more in the spirit of the sport are the back-to-back inverted 1080s that Kass pioneered--which use every trick in the Isaac Newton playbook.